Macro to replace cells value automatically based on another cell change event

I know there are several threads but I wasn't able to find something which will fit my needs.
I have a sheet in which I want to Find & Replace cell values based on the cell $B1 which will be a drop down list. Also I need to mention that the cells which I want to replace the string have formulas. Here's an example of what a cell looks:
=IF('http://sharepoint.www.com/Industrial Engineering/2011.06 June/[Workbook.xls]June'!I218=0,"",'http://sharepoint.www.com/Industrial Engineering/2011.06 June/[Workbook.xls]June'!I218)

By changing the value from $B1 from Workbook to Workbook1 I want to automatically replace in a specific range the values from the cell: Workbook.xls with Workbook1.xls

I have a code which will work but I need to narrow down the replace function to a specific range like $A2:$BA250

My macro looks like this:

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
  Dim txtW As String
  txtW = Range("$H$13").Value
  Dim txtR As String
  txtR = Range("$B$1").Value
If Target.Address = "$B$1" Then

Cells.Replace What:=txtW, Replacement:=txtR, LookAt:= _
    xlPart, SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
    ReplaceFormat:=False

    Else
Range("$b$1").Select
    End If
End Sub

Please add code tags to your OP, as in the following code example.

I think you might be better with this, also untested

    Range("A2:BA250").Replace What:=txtW, Replacement:=txtR, LookAt:= _
    xlPart, SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
    ReplaceFormat:=False

Regards

You're welcome. Thanks for the feedback and rep.

Please go back to your original thread and add Code Tags. According to the forum rules, we should not really have provided an answer unless you comply with the rules. The Moderators are quite strict about applying the forum rules and we could all be reprimanded for not following them. It's a small price to pay to make this a useful repository of knowledge.

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Regards